hdu 4901

计数dp

做不出来真是惭愧。。。

#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <stack>
#include <vector>
#include <sstream>
#include <cstring>
#include <string>
#include <map>
#include <set>
#include <queue>
#include <algorithm>
#include <iostream>
#define FFI freopen("in.txt", "r", stdin)
#define maxn 200010
#define INF 0x3f3f3f3f
#define inf 10000000
#define MOD 1000000007
#define ULL unsigned long long
#define LL long long
#define _setm(houge) memset(houge, INF, sizeof(houge))
#define _setf(houge) memset(houge, -1, sizeof(houge))
#define _clear(houge) memset(houge, 0, sizeof(houge))

using namespace std;

LL f[1100][1100], g[1100][1100], h[1100][1100];
int a[1100], n;

void init() {
    _clear(f);
    _clear(g);
    _clear(h);
}

void dp() {
    f[1][a[1]] = 1;
    for(int i = 2; i <= n; ++ i) {
        f[i][a[i]] ++;
        for(int s = 0; s < 1024; ++ s) {
            f[i][s^a[i]] += f[i-1][s];
            f[i][s] += f[i-1][s];
            f[i][s^a[i]] %= MOD;
            f[i][s] %= MOD;
        }
    }

    g[n][a[n]] = h[n][a[n]] = 1;
    for(int i = n-1; i >= 1; -- i) {
        g[i][a[i]] ++;
        h[i][a[i]] ++;
        for(int s = 0; s < 1024; ++ s) {
            g[i][s&a[i]] += h[i+1][s];
            h[i][s&a[i]] += h[i+1][s];
            h[i][s] += h[i+1][s];
            g[i][s&a[i]] %= MOD;
            h[i][s&a[i]] %= MOD;
            h[i][s] %= MOD;
        }
    }
}

int main()
{
    int t;
    scanf("%d", &t);
    while(t --) {
        scanf("%d", &n);
        for(int i = 1; i <= n; ++ i) {
            scanf("%d", &a[i]);
        }
        init();
        dp();
        LL ans = 0;
        for(int i = 1; i < n; ++ i) {
            for(int j = 0; j < 1024; ++ j) {
                ans = (ans+f[i][j]*g[i+1][j])%MOD;
            }
        }
        printf("%I64d\n", ans);
    }
    return 0;
}